Lever mechanism for control instruments



J. 23 1951 E. c. BURDKCK LEVER MECHANISM FOR CONTROL INSTRUMENTS Original Filed Oct. 22, 1942 3 Sheets-Sheet l XNVENTOR. EDWIN CLARK k I /Ny,-- &

BURDICK ATTORNEY Jan. 23; 1951 E. c. BURDICK 2,539,117

LEVER MECHANISM FOR CONTROL ms'mumsn'rs Original Filed Oct. 22, 1942 3 Sheets-Sheet 2 FIG. 2 iw fil' mvmrog. EDWIN CLARK BURDICK.

ATTORNEY.

Jam 23,, 519511 E. c. BURDICK LEVER MECHANISM FOR CONTROL ms'mmmms 5 Sheets-Sheet 3 Original Filed 001:. 22, 1.942

' I I ll'llll K m D ma m T N MB A R WM 04 m L C M w a D E Y B 6 L 4 5 5% l 7 6 o. PFIMY. fi 7 8 Patented Jan. 23, 1951 LEVER MECHANISM FOR CONTROL INSTRUMENTS Edwin C. Burdick, Philadelphia, Pa., asslgnor, by mesne assignments, to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Original application October 22, 1942, Serial No. 462,950. Divided and this application March 12, 1946, Serial No. 653,889

9 Claims. 1

The present invention relates to instruments for automatically controlling the value of some, condition, and more particularly to controlling the ratio of the value of one condition with respect to the value of another condition. In the following description of the invention the primary condition will refer to the uncontrolled condition and the secondary condition will refer to the condition whose value is kept at some predetermined value with respect to that of the primary condition. y

It will be obvious to those skilled in the art that the primary measuring elements that are responsive to the value of the conditions being measured and serve to adjust the control instrumentalities may be responsive to any measurable condition such as flow, temperature, pressure, or liquid level. For purposes of this description, however, the invention will be described as being used in a flow control system.

It is often necessary to control the value of one condition to a certain proportion of a sec-- pnd condition or to maintain the ratio between the two conditions constant. It is, accordingly, an object of the invention to provide an instrument which will exactly maintain one condition at a given ratio with respect to a second condition.

It is a further object of the invention to provide a pneumatic control instrument which is remotely actuated in response to the value of one condition to control the value of a second condition. It is a further object of the invention to provide an instrument which may be used to determine and control the ratio of the flow of a fluid through one conduit with respect to the flow through another conduit.

The present application is a division of my application Serial Number 462,950, filed October 22, 1942 now Patent 2,410,335, issued October 29, 1946. That application is more particularly related to the control features of the instrument and the controlling of a variable condition, whereas the present application is directed more particularly to the leverage system which is used in the ratio control unit.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification For a better understanding of the invention, however, its advantages and specific objects obtained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of the invention.

In the drawings:

Figure 1 is a view of the upper part of an instrument embodying the invention,

Figure 2 is an enlarged view of the ratio control umt,

Figure 3 is a top view of Figure 2,

Figure 4 is an enlarged view of an adjustable part used in Figure 2,

Figure 5 is a top view of Figure 4,

Figures 6 and 7 are front and top views of an alternative adjustable connection,

Figure 8 is a view on line 8-8 of Figure 7,

Figure 9 is a diagrammatic view showing a fiow ratio control system,

Figure 10 is a view showing in detail some levers used in Figure 2, and

Figure 11 is a view of a modified type of ratio adjusting mechanism.

Referring first to Figure 9, there is shown a pipe I through which a fluid, known herein as the primary fluid, flows. There is also shown a pipe 2 through which a fluid, known herein as the secondary fluid, flows and which is to be controlled to some value that retains a given ratio with respect to the primary fluid flow at all values of flow of the latter. To this end the pipe I is provided with an orifice 3 from opposite sides of which pressure taps 4 and 5 are taken and which lead to a fiow measuring instrument 9. This instrument, which may take the form of any well known flow meter and is shown herein as an indicator is provided with a device that sets up an air pressure which is proportional to the value of the fiow being measured. Such an instrument is shown and described in the application of Coleman 3. Moore, Serial No. 173,008, filed on November 5, 1937 now Patent 2,311,853, issued February 23, 1943. The instrument 5 is supplied with air under a regulated pressure through a pipe I and modulates the air in accordance with the flow in pipe I and supplies this air through a pipe 8 to an instrument 9.

The pipe 2 is provided with an orifice II, the opposite sides of which are connected by pres- 2 suretaps II and |2totheinstrument2which may be provided with any conventional type of flow measuring device. The instrument 2 is also provided with a control mechanism that may be of any conventional type, but is preferably of the pneumatic type known as the Brown Air-O-Line Controller such as is disclosed in the patent of through the pipe 2 it Coleman B. Moore 2,125,081 dated July 26, 1938. I

The instrument 2 is supplied with air under a regulated pressure through pipe I2 and delivers air at variable pressures through a pipe I4 to a pneumaticecontrol valve II in the secondary flow line 2. The instrument 2 therefore controls the flow in pipe 2, and this instrument has its control point adjusted pneumatically by air supplied through the pipe 2 to keep the flow in pipe 2 at some particular ratio with respect to the flow in pipe I.

The instrument 2 is provided with a shaft I2 that is rotated to various positions depending upon the flow through the pipe 2. This shaft can be rotated by any suitable flow measuring instrument such as the float in a differential pressure manometer, and it serves to move a pen which gives a record of the value of the flow, and to adjust the control mechanism which serves to regulate the flow in the pipe 2. The shaft II has attached to it an arm I1, and has free upon it an arm II which is adjustably connected to the arm I1 for movement therewith. To this end the arm I1 is provided with 9. turned up portion .I2, and the arm I2 is provided with 9. turned up portion 22 between which portions is placed a spring 2|. This spring serves to hold the arms I1 and I2 apart a distance that is adjusted by means of a screw 22 which extends through the portion 22, and is threaded into the portion l2. By rotation of the screw, the angular relation between arms I1 and I2 may be changed. The outer end of the arm I2 is provided with a slot 22 in which is adjustably mounted a slider 24 which carries the lower end of a link 25. The upper end of this link is pivoted to the outer end of an arm 24 that is fastened to a pen shaft 21. Therefore, as the shaft I2 rotates, the shaft 21 will be rotated proportional amounts to move a pen arm 22, which is attached to the shaft. back and forth across a chart 22 to make a record of the flow through pipe 2. This chart is rotated at any desired speed by means of the chart hub 24.

The shaft 21 also serves to adjust the control mechanism of the instrument 2. To this end. the shaft 21 is provided with an arm 2| that has the upper end of a link 22 attached to its outer end. The lower end of link 22 is fastened to a differential lever 22 that is pivoted to move around point 24. Attached to the mid-point of the lever 22 is the upper end of a connecting link 22 which serves toadjust the control mechanism 22 that is shown in dotted outline. The lower end of the link 25 is connected to a lever 21 which is pivoted at 22 and which serves to move a flapper 22 relative to a bleed nozzle 42. The control mechanism 22, which preferably takes the form of the control mechanism shown in the above entioned Moore Patent 2,125,081, serves to adj t the air pressure supplied through pipe I4 to the control valve I5 as the flapper 22 is moved relative to the nozzle 42 in a manner which is fully described in the said patent, and

which is well known commercially.

In order to change the control point of the mechanism 22 or to change the value at which this instrument will serve to maintain the flow is necessary to shift the pivot point 24 of the differential lever 22. To this end, the pivot 24 is formed on the outer end of a lever 4| that is pivoted to move around a supporting shaft 42. This lever is provided with an index member 42, that cooperates with the chart 22 to indicate the value at which the instrument will tend to maintain the flow. The lever 4| and its pointer 42 are moved around the shaft 42 by means of a link 44 that is adjusted in accordance with the flow through the pipe I. Simultaneously with the adjustment of the lever 4|, a pen arm 45 is also moved across the chart 22 to make a record of the flow through the pipe I. This penarmisattachedto ashaft 44 thatis moved by means of a driving arm 41 and a driving link 42. The link 44 and the driving link 42 are'simultaneously moved by a ratio control unit 52 that is located in the upper left end corner of the instrument 2, and the details of which will be presently described. It is noted that the pen arm 45 is moved directly in proportion to the flow in pipe I, while the index pointer is moved at some predetermined ratio with respect to the flow in said pipe. In order to limit the adjustment of the control point of the instrument 2 to prevent the flow through pipe 2 from being moved beyond predetermined limits, this instrument is provided with stops 42 and 52 that are pivoted at 42, and which are adapted to be engaged by an abutment 5| on the lever 4|. The stops may be adjusted to various positions around their pivot to limit the movement of the abutment, and thereby of the arm 4|.

Air under a variable pressure is supplied by the instrument 2 through the pipe 8 to a chamber 53 which is formed in the ratio control unit 52. This chamber is formed between a cupshaped casing 54 and a bellows 55, both of which are fastened at their upper ends to a supporting casting 56. The bellows 55 is normally biased in a direction to elongate it to keep the chamber 52 at its minimum volume, by means of a spring 51 that has its upper end engaging an abutment formed on the casing 52 and has its lower end engaging a socket 52 that is attached to the end wall of the bellows. A change in the length of the bellows produced by a change in pressure in the chamber serves to move directly the pen 45 across the chart 22 by means of a rod 52 whose lower end engages in the socket 52 and whose upper end is attached to a lever 5| which is fastened to the rotatable shaft 22. The connection between rod. 52 and lever 5| consists of a slider 80 that is provided with turned up ends which engage the threads of a screw 2Ia which is rotatable in a bracket attached to the lever 2|. Rotation of screw Bla will move the slider toward or away from shaft 22. Also attached to the shaft 62 is an arm 22 which serves to move a second arm 64, that is free on the shaft, through an adjustable connection 65 which is similar to the connection previously described between arms I1 and II. A spring 82 encircles the shaft 22 and serves to bias this shaft and the parts attached thereto in a clockwise direction in order to maintain the lower end of the rod 52 in engagement with the socket 52 and to prevent play between these parts.

As the pressure in the chamber 52 changes, the bellows 55 will be elongated or contracted and will operate through the rod 52, lever 6| arm 42, and arm 24, and the driving link 42 to move the pen 45 across the chart 22 in accordance with the value of the flow through pipe I. The ac arm to part and thereby regulate the amount that the pen is moved for a given pressure change in the chamber 58. .The adjustment 85 is used to vary the relative positions of arms 83 and 88 and thereby determine the zero position of the pen arm or the position that the pen arm will assume over the chart for any given pres-'- sure applied to the chamber 58.

Movement of the bellows 55 also serves to shift the lever II to adjust the control point of the instrument 8 various amounts for a given pressure change in the chamber 58. To this end there is provided a push rod 81 that is attached at its lower end to the rod 58 at the point 88. The upper end of the rod 81 is pivoted to an adjustable block 88 at point 18. This block (see Figures 4 and 5) consists of a pair of plates II and I2 which slidabiy receive between them a lever 18 that is pivoted at I4. The block is held in a given position relative to the lever 18 by means of a spring I5 which tends to pull the block upwardly until the lower edge of lever I8 is engaged by a pin I8 that extends between the plates II and 12. The block can be adjusted along lever I8 toward and away from the pivot and an is a driving member 19 that has a straight upper surface. This member serves to move a driven member 82 by means of a force transmitting member or slider taking the form of rollers 88 which extend between the parts I8 and 82 as best shown in Figures 3 and 10. The driven member 82 is mounted for movement up and down without changing its angle to the horizontal, and to this end is attached to a shaft 88 which is supported by an arm 85 that is pivoted on a rotatable shaft 88. Also fastened to the shaft 84 is a vertical member 81 whose lower end has pivoted to ,it an arm 88 which is pivoted to the casting 58 at 88. Arms 85 and 88 along with the member 81 form aparallel lever arrangement so that as the driven member 82 is moved up or down, its angularity will not be changed. A spring 88 extends between the lower end of the member 81 and the casting and serves to take up backlash between the parts so that there will be no play as the unit is operated. a

Movement of the member 82 is used to set the control point of the instrument 8. As is noted above, the part 85 is free of the shaft 88, but transmits motion to that shaft by means of engagement between 85 and the bent over end 8| of the lever 82 which is attached to the shaft 88. The end SI and the member 85 are held in engagement with each other by means of a spring 88. The outer or front end of shaft 88 has attached to it an arm 94 and has free on it an pressure in the chamber 58 can be used to move, the lever 4| through the operating connections which have been described above. In order to vary the positon of the lever ll, for a given length of the bellows, the adjustable connections 88 are used. To facilitate this adjustment, the lower end of arm 88 is provided with a pointer 81 that cooperates with a scale 88 which is formed on the arm 85. It is noted that a spring 88 surrounds shaft 88 and acts between the casting 58 and lever 85 to bias the assembly in a clockwise direction in Figure 3 in order to keep parts 82, :8 and "I8 in engagement with each other at all imes. The amount of movement of the member 82 and, therefore, the amount of control point ad- .iustment that is given to the instrument 8 for a given pressure change in the chamber 55 is varied by moving the roller 88 along members I8 and 82. To this end, the roller 88 is connected by means of a link I88 with acarriage I8I that is arm which arms are adjustably connected for supported by guide rods I82 which project from the side of thecasting 58. The carriage is shifted along its guide rods by means of a link I88 that is connected at one end to the carriage, and at its'other end .to a gear sector member I84 which is attached to' a shaft I85. This sector may be rotated by means of a pinion I88 that is mounted on a shaft I81, whichshaft has a knob I88 on its front end. The shaft I81 is shown as extending through a supporting plate of the instrument with the knob I88 in a position to be accessible from the front. of the supporting plate. By mounting the adjusting knob away from the levers I8 and 82 there is no possibility of disturbing the positions of the levers and therefore upsetting the control as the roller 88 is adjusted along them to vary the ratio of the system. A spring I88 is provided to take up .any back lash that may appear in the train of mechanism. To indicate the positon of the roller 88 between parts I8 and 82 a pointer H8 is attached to the front end of shaft I85 and is moved by it across a scale I I I that is attached to a chart backing plate of the instrument.

When the flow in pipe I is zero the flow in pipe 2 should also be zero regardless of what ratio the latter is to have with the former. Therefore, when the flow in pipe I is zero, and member 18 is in its zero position, the roller 88 may be moved from one end to the other of member 18 without changing the position of member 82. In order to insure that this will be the case the member 82 is adjusted on shaft 88 until its lower surface is parallel to the upper surface of member I8, and is then fastened in this position on the shaft. It is noted that by maintaining the member 82 in the same angular position on the shaft 84 to which it was adjusted, while raising and lowering the member, that the calibration of the unit 52 will be linear. That is, the member 82 will be moved equal amounts for equal adjustments of roller 83 along the member I8 for any position of the latter but its zero position. The desirability for such a calibration should be obvious, since no matter what the characteristics of the condition being measured may be, they will be exactly reflected in the adjustment of the control point adjusting lever I I.

In the operation of a control system embodying the present invention, the primary flow through pipe I is measured by and indicated by means of the instrument 8, which instrument sets up a variable pressure in the pipe 8 proportional to the value of the flow. This pressure is applied asaanv chart 29 and at the same time will operate througharm 3| to adjust the control mechanism 88. If it is desired to vary the ratio that the secondary how has with respect to the primary flow, it is only necessary to rotate the knob I08 to shift the roller I! along member 19. It will be seen that the instrument 9 has recorded on its chart 29 the values of both of the flows. Also clearly visible from the front of the instrument is the control point to which the flow in pipe 2 is being regulated as well as the ratio which is being maintained between the two flows. A complete picture of the entire control system is therefore readily obtained by inspection of a single instrument. The ratioing unit 52 of the instrument 9 is, for example, designed to move the secondary control pointer 43 from to 200% of the reading of the primary measuring instrument I as shown by the calibration marks on the scale I I I. That is, when the unit 52 is adjusted for the lower limit of 25% movement of the pointer, the ratio mechanism will position the control pointer 43 at 25% of full scale when the primary flow in pipe I is at a maximum. When the unit 52 is adjusted for the upper limit of 200% movement,

the mechanism will position the control pointer 43 at 100% of full scale movement when the flow through pipe I is at of its maximum value; The significance of these adjustments will now be considered.

As is well known, the actual ratio of the secondary ilow'to the primary flow, of course, depends upon the sizes of pipes 2 and I and their respective orifices III- and 3. The controller 9 can then vary this basic ratio from 25% to 200%. This can best be explained by a typical example.

Assume that the two flows in pipes 2 and I have a basic ratio of 5 to 1; the secondary ilow in pipe 2 having an average value of 375, and the primary flow in pipe I having an average value of '75 units. The range for the primary meter 6 will then be 0 to 100 units and the range for the secondary meter will be 0 to 500 units.

Since the flow through the primary pipe I isrecorded by the pen 45 on the chart 29 in instru-.

ment 9 this pen will read /100 or 75% of full of the flow would mean that the secondary should 6 have an average value of 450 units. Since the primary flow is recorded on the secondary chart 2! as 375 units, the ratio setting necessary to maintain the new basic ratio of 6 to 1, therefore, must be /115x100 or 120% of the primary pen reading. To maintain this ratio the pointer III! will be adjusted to 120 on the scale III. The limits to which the basic ratio of 51:0 1 could be 59 along the lever SI.

8 varied would be from 25% to 200% of the basic ratio of5to lorfrom 1.25to1to 10to 1.

In the above description, the adjustment that has been made by the ratio flow control imit I! has been a direct one. In other words. an increase in the primary flow has been used to move the control point of the secondary controller I upscale. In some cases, it may be desirable to have an inverse ratio or to move the control point of the instrument 9 down scale as the primary flow increases. In such an event, it will be necessary to connect the link 44, which extends from arm 85, to lever 4| at a point which is above the pivot 42 instead of below the pivot as is shown in Figure 1. This is a minor change and can be done without any appreciable alteration of the various parts.

In some instances, it may be desirable to have the ratio between the flows kept at some predetermined amount plus or minus an additional number of units of the secondary flow. By the proper operation of adjustment 96, this may be accomplished. If the pointer 91 is moved to the zero mark on scale 58, the pointer 43 will be moved to the zero mark on the chart 2! when In Figures 6, 7, and 8 there is shown an adjustable connection which may be used between rod 59 and lever 6| in place of that shown at I in Figure 2. In this connection, the lever 6| is provided with an opening BIA that receives the ends of a slider H2 and a. clamping member III. A screw II4 that receives the upper end of rod 59 on a shoulder formed on its head passes through slider II! and the opening CIA, and is threaded in the clamp member III. When this screw is tightened down, the clamp member serves to prevent movement of the slider and rod In order to adjust the rod 59 toward and away from the fulcrum on lever GI, there is provided a screw II! which extends through an opening II8 formed in a bent over end of the lever BI. This screw freely through the open ng, but is threaded into the ends of the slider II! and clamp H3. Rotation of the screw will therefore move the slider and clamp in one direction or the other to properly position the rod 59. In the operation of this adjustment, the screw III is first loosened and then screw I I5 is rotated to give the proper adjustment. Thereafter, the screw I I4 is tightened to hold the parts in their adjusted position. The opening I I6 is made in the shaft shown in Figure 8 in order that the screw may pass through this opening and may be loose during the time that the adjustment is made.

In the above description of the control system, it was assumed that the ratio between two flows in pipes I and 2 would be adjusted manually by' rotation of the knob I08. In some cases it is desirable to adjust the ratio between the flows through the two pipes I and 2 in response to the variations in the value of another condition. This may be accomp ished in the manner shown in Figure 10 in which the right end of link that controls the position of roller II is attached to one arm of a bell crank III. The bell crank is pivoted at II! to a casting III, and has 15 on its other arm a rod I20 which engages a socket IN attached to the end wall of a bellows I22. This bellows forms one wall of a chamber I29 similar to the chamber I2 in the unit 02. The other wall of this chamber is formed by a casing member I24 which is provided with an opening through which a tube I25 may be connected with the chamber.

When the ratio is to be changed in accordance with the value of a third variable condition, and that condition is measured by some suitable instrument such as that described in the above mentioned Moore Patent 2,311,853, that instrument serves to set up an air pressure proportional to the value of the condition which pressure is applied to the chamber I 29 to vary the length of bellows I22. As the bellows varies. in length, it shifts the roller 93 between members It and 92 to adjust the ratio between the primary and secondary flows in a manner that has previously been described.

The ratio control unit 52 which has been described above was adjusted by means of a knob which was placed in an accessibleposition on the instrument. In some cases, it may be desirable to have the unit self-contained with the adjusting means on the unit instead of being mounted on another portion of the instrument. Such a construction is shown in Figure 11 which operates in exactly the same manner as that previously decsribed, with the exception of the way the ratio adjustment is made. In the embodiment of Figure 11, the rod 61 extending up from the bellows 55 serves to move a lever I25 that is attached to a shaft I2'I which is :Iournaled in the casting 56. Between the rod 61, and the lever I there is shown an adjustable connection I28 which is similar to the connection 60 but which may be similar to that shown at 69 or to that shown in Figure 6. Movable with the shaft I21 is an arm I29 upon which is mounted a slider I30 that carries a roller I3I which serves to move the member 82. Therefore, as the rod 61 is raised and lowered due to pressure changes in chamber 53, the arm I29 will be moved to raise and lower roller I 3| to change the position of member 92. In order to vary the ratio of movement of member 82 with respect to arm I29, the slider I 30 is providedwith a pinion I32 that engages with a rack I33 formed on the upper surface of arm I29. The pinion is rotated by means of a knob I34 to shift the slider I30 toward and away from the shaft I21. In order to facilitate a proper adjustment of the slider along the arm, the slider is provided with a pointer I35 that coo erates with a scale formed on the arm I29. This scale may be calibrated in exactly the manner as the scale III which was shown in Figure 2. It is noted that in Figure 11, the connection between arm 95A and shaft 86 is formed to the left of the shaft instead of to the right as in Figure 2. To this end, arm 95 is extended to the left of the shaft 96, and is engaged by a bent over portion 9IA on the arm 92A, which parts correspond respectively to parts 9| and S2 in Figure 2. The operation of this embodiment of the invention is exactly the same as that previously described.

From the above description, it will be seen that I have provided a simple unit which can be used, to adjust the control point of a control instru-T ment in accordance with any desired ratio that; is to be produced between the two units. While,

the unit has been described as being capable of varying the ratio between the primary and secondary conditions from 25 to 200 percent it will be obvious that these limits were arbitrarily chosen and that others could be used in place thereof. It is also of advantage to have a record of both conditions on the same chart along with an indication of the value at which it is desired to keep the secondary condition. This, coupled with the fact that the present instrument is provided with a pointer that shows the ratio which is being maintained tween the conditions, makes the instrument mely complete.

While in accordance wi statutes, I have illustrated and described the best form of my invention now known to me, it will be apparent to those skilled in the art that certain changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claims, and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

-Having now described my invention, what I claim as new and desire to secure by Letters Patent is: v

1. In a control instrument having a control unit that is used to adjust the value of a condition, said instrument having control point adjusting means, mechanism to adjust the control point adjusting means of said unit comprising a pressure responsive device, a pivoted lever, means operated by said device to move said lever around its pivot, a member having an edge, means to mount said member for parallel movement so that as said member moves said edge will remain in the same, angular position, a force transmitting part located between said pivoted lever and the edge of said member, means to move said part along said lever and edge so that said member will be moved different amounts for the same angular movement of said lever, means to transmit movement of said member to said control point adjusting means, and means to indicate the position of said force transmitting part.

2. In a control instrument having control point adjusting means and including a part moved as the control point is adjusted, a responsive device moved to various positions depending upon the value of a condition, a first pivoted lever, a second pivoted lever, a member carried by said second lever and having an edge thereon, means to hold said member on said second lever in a manner so that said edge is always at the same angular position with respect to the horizontal as said second lever moves, a slider extending between said flrst lever and said edge, means to 'shift said slider to various positions between said first lever and said edge, means to move said first lever by said device and therefore said second lever an amount, for a given movement of said device, depending upon the position of said slider, and means to connect said part for movement by said second lever.

3. In a control instrument, control point adjusting means to set the value at which the control instrument, when operative, will maintain the controlled variable, said control point adjusting means including a part moved as the control point is adjusted, means to move said part including a pressure responsive member, a pair of cooperating levers, a slider between said levers and operating to transfer movement of one lever to the other in an amount depending upon the position of said slider relative to said levers, means to move said one of said levers by said pressure responsive member, connecting means between said other lever and said part, and means to adjust said connecting means so the provisions of the I 11 that said part may have ditl'erent positions for a given position of saidother lever.

4. In a control instrument, control point adjusting means to set the .value at which the control instrument, when operative, will maintain the controlled variable, said control point adjusting means including a part moved as the control point is adjusted, a member movable to various positions depending upon the value of a condition, a pair of cooperating oppositely disposed levers. a motion transmitting slider between said levers, said member acting on one lever of said pair of levers to move said one lever and through said slider the other lever of said pair of levers an amount depending upon the relative positions of said slider and pair of levers, and means extending between saidother lever and said part including mean to move said part to various positions for a given position or said other lever.

5. In a control instrument having control point adjusting means and including a part moved as the control point is adjusted, a device moved to various positions depending upon the value of a primary condition, a lever system'including a first pivoted lever, a second pivoted lever, a member carried by said second pivoted lever and having an edge thereon, means to attach said member to said second pivoted lever in such a manner that said edge remains at the same angle to the horizontal as said second pivoted lever moves around its pivot, a force transmitting element extending between said first pivoted lever and said edge of said member, means responsive to the value of a third variable condition operative to shift said element to various positions between said first lever and said edge, means operated by said device to move said first pivoted lever, and through said element and member, said second pivoted lever an amount proportional to said primary condition and varying in accordance with the position of said element, and means to connect said part for movement by said second lever.

6. In a control instrument, control point adjusting means to set the value at which the control instrument, when operative, will maintain the controlled variable, said control point adjusting means having a part moved to various positions as the control point of the instrument is adjusted, means to move said part including a first pivoted lever moved in response to changes in a condition, a second movable lever, an adjustable slider between said levers to transfer movement of one to the other in amounts dependent upon the position of said slider, a lever arm rotated by said second movable lever, a connecting link extending between said lever arm and said part, and means to shift said connecting link relative to said lever arm whereby said part may be moved to difl'erent positions fora given position of said first pivoted lever dependent upon the position of said slider and of said connecting link relative to said lever arm.

7. In a control instrument, control pointadjusting means to set the value at which the ill control instrument, when operative, will maintain the controlled variable, said control point adjusting means having a part moved to various positions as the control point oi. the instrument is adjusted, a member movable to various positions depending upon the value of a condition. a pair of cooperating oppositely disposed levers, an adjustable slider disposed between said levers, said member acting directly on one of said levers, and through said slider the other of said levers to move said other lever an amount dependent upon the position of said slider for a given movement of said member, a first arm moved by said other lever, a second arm, connecting means between said second arm and said part, and means to attach adjustably said arms for movement together whereby said part may be moved to different positions for the same position of said other lever.

B. In a control instrument, control point adjusting means to set the value atwhich the control instrument, when operative, will maintain the controlled variable, said control point adjusting means including a part moved as the control point is adjusted, means to move said part including a pressure responsive member, a lever system extending between said member and said part, said lever system including means to vary the amount of movement of said part for a given movement of said member and means to vary the position of said part for a given position of said member.

9. In a control instrument having control point adjusting. means including a part having limits of movement and moved as the control point is adjusted, means to move said part including a pressure responsive member, connecting means between said member and part including a first and a second pivoted lever, a thrust pin between said levers whereby movement of one lever will be transferred to the other, an arm, strain release means between said arm and said second lever, and a connection between said armand part whereby if said member moves in one direction to move said part to one oi! its limits or travel said thrust pin and one of said levers will separate and if said member moves in the opposite direction to move said part to its other limit said strain release will permit said arm and second lever to move relative to each other.

EDWIN C. BURDICK.

REFERENCES CITED The following references are of record in the die of this patent: I

UNITED STATES PATENTS Newell Nov. 23. 1943 

